This invention concerns the manufacture of nonplanar product for absorbing body fluids and, in particular, concerns methods for making sanitary napkins and other absorbent products designed to be worn in the perineal area of the body including for example, panty liners, panty shields, incontinence pads, diapers and the like.
Traditionally such products comprise generally planar pads of absorbent materials having, on the side of the product intended to be worn against the body, a body fluid pervious cover adapted to permit the flow of body fluid, e.g., menses or urine, from the body to the absorbent pad. The opposite or garment facing side of the pad is generally provided with a body fluid impervious cover to insure that such body fluid absorbed by the pad does not stain or otherwise flow onto the undergarment of the wearer. When such products are placed against the body and inside the crotch portion of an undergarment they deform and take the arcuate shape of the body with the body facing side of the product being concave and the garment side being convex.
Unfortunately, since the garment side cover of prior products is generally inelastic and hence cannot lengthen, the napkin, in assuming this shape, does so by virtue of having the cover on the body facing side shorten. This shortening is accomplished by forming wrinkles or pleats on the body facing side of the product. To a degree, the absorbent pad also forms wrinkles or pleats on this side of the product. These wrinkles or pleats are highly undesirable in that they cause user discomfort and also create transverse channels allowing body fluid to bypass the product and leak from the longitudinal sides onto the undergarment.
The problem associated with planar body fluid absorbent products is particularly aggravated when the absorbent pad is comprised of a resilient material, i.e., one with elastic memory, such as for example, absorbent polymeric foam. In this instance, the product when placed against the body in conformance with the body contours will then tend to straighten out and return to its original planar shape to the degree that the constraining body and undergarment surfaces will allow. The result is that only a small portion of the product remains in intimate contact with the body with a large portion of the product standing away from the body causing user discomfort, possible failure by leakage and even embarrassing visibility through the user's garments.
Several suggestions already exist in the prior art for providing body fluid absorbent products manufactured in an arcuate shape which tend to obviate the above problems with respect to planar products. Thus, for example, in U.S. Pat. No. 3,236,238 issued to E. A. Morse on Feb. 22, 1966, a curved sanitary napkin is disclosed which incorporates a body facing cover having heat shrinkable elements therein which, upon shrinking, cause the napkin to curve. In U.S. Pat. No. 3,262,451 issued on July 26, 1966 to E. A. Morse, a curved sanitary napkin is disclosed which incorporates, in the absorbent pad, a heat shrinkable element which, upon shrinking, causes the napkin to curve. In U.S. Pat. No. 2,964,039 issued on Dec. 13, 1960 to R. W. Johnson, Jr., et al. a curved sanitary napkin is suggested which comprises a curved, molded, absorbent pad, such pad being stabilized in the curved form. In U.S. Pat. No. 3,445,897 issued to N. J. Franz on May 27, 1969, a method of making a wrapped curved napkin from a preshaped napkin core is disclosed. These prior suggestions have, in the main, failed to be commercialized primarily because they require relatively exotic raw materials or unusual and difficult processing steps, incompatible with the high speed production of the relatively inexpensive products designed to be discarded after a single use.
Accordingly, there is a need for a relatively simple process for manufacturing curved absorbent products to obviate the problems associated with planar products without the complexity and expense inherent in the prior suggestions.